Catheter with contractable mapping assembly

ABSTRACT

The invention is directed to a mapping catheter useful for mapping tubular regions in and around the heart. The catheter comprises an elongated tubular catheter body. A mapping assembly is provided at the distal end of the catheter body. The mapping assembly comprises a tubular structure comprising a preformed generally circular main region generally transverse and distal to the catheter body and having an outer circumference. The tubular structure comprises a non-conductive cover over at least the main region of the mapping assembly. A plurality of electrodes are carried by the generally circular main region of the mapping assembly. A control handle is mounted at the proximal end of the catheter body. A contraction wire extends through the catheter body and non-conductive cover of the mapping assembly for contracting the generally circular main region of the mapping assembly. The contraction wire has a distal end anchored in the non-conductive cover and a proximal end anchored to a mechanism in the control handle that facilitates longitudinal movement of the contraction wire relative to the catheter body. The portion of the contraction wire extending through the non-conductive cover is positioned on the side of the generally circular main region closer to the center of the generally circular region.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/512,620, filed Aug. 29, 2006 and entitled CATHETER WITH CONTRACTABLEMAPPING ASSEMBLY which is a continuation of U.S. patent application Ser.No. 10/386,872, filed Mar. 12, 2003 and entitled CATHETER WITHCONTRACTABLE MAPPING ASSEMBLY (now U.S. Pat. No. 7,142,903) the entirecontents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an improved mapping catheter that isparticularly useful for mapping electrical activity in a tubular regionof or near the heart.

BACKGROUND OF THE INVENTION

Atrial fibrillation is a common sustained cardiac arrhythmia and a majorcause of stroke. This condition is perpetuated by reentrant waveletspropagating in an abnormal atrial-tissue substrate. Various approacheshave been developed to interrupt wavelets, including surgical orcatheter-mediated atriotomy. Prior to treating the condition, one has tofirst determine the location of the wavelets. Various techniques havebeen proposed for making such a determination. None of the proposedtechniques, however, provide for measurement of the activity within apulmonary vein, coronary sinus or other tubular structure about theinner circumference of the structure.

SUMMARY OF THE INVENTION

The present invention is directed to a catheter having a mappingassembly and a method for measuring electrical activity within a tubularregion of or near the heart, e.g., a pulmonary vein, the coronary sinus,the superior vena cava, or the pulmonary outflow tract.

In one embodiment, the invention is directed to a mapping catheteruseful for mapping tubular regions in and around the heart. The cathetercomprises an elongated tubular catheter body. A mapping assembly isprovided at the distal end of the catheter body. The mapping assemblycomprises a tubular structure comprising a pre-formed generally circularmain region generally transverse and distal to the catheter body andhaving an outer circumference. The tubular structure comprises anon-conductive cover over at least the main region of the mappingassembly. A plurality of electrodes are carried by the generallycircular main region of the mapping assembly. A control handle ismounted at the proximal end of the catheter body. A contraction wireextends through the catheter body and non-conductive cover of themapping assembly for contracting the generally circular main region ofthe mapping assembly. The contraction wire has a distal end anchored inthe non-conductive cover and a proximal end anchored to a mechanism inthe control handle that facilitates longitudinal movement of thecontraction wire relative to the catheter body. The portion of thecontraction wire extending through the non-conductive cover ispositioned on the side of the generally circular main region closer tothe center of the generally circular region.

In another embodiment the invention is directed to a mapping cathetercomprising an elongated tubular catheter body having an outer wall andproximal and distal ends. A mapping assembly is provided at the distalend of the catheter body. The mapping assembly comprises a tubularstructure comprising a pre-formed generally circular main regiongenerally transverse and distal to the catheter body and having an outercircumference. The tubular structure comprises a non-conductive coverover at least the main region of the mapping assembly and a pre-formedsupport member extending through a plastic tube that extends through thenon-conductive cover. A plurality of electrodes are carried by thegenerally circular main region of the mapping assembly. A control handleis mounted at the proximal end of the catheter body. A contraction wireextends through the catheter body and through the plastic tube withinnon-conductive cover of the mapping assembly for contracting thegenerally circular main region of the mapping assembly. The contractionwire has a distal end anchored in the non-conductive cover and aproximal end anchored to a mechanism in the control handle thatfacilitates longitudinal movement of the contraction wire relative tothe catheter body. The portion of the contraction wire extending throughthe non-conductive cover is positioned on the side of the generallycircular main region closer to the center of the generally circularregion. A deflection wire also extends through the catheter body. Thedeflection wire has a distal end fixedly attached to the catheter bodynear the catheter body's distal end and a proximal end anchored to amechanism in the control handle that facilitates longitudinal movementof the deflection wire relative to the catheter body.

In another embodiment, the invention is directed to a method for mappingelectrical activity within a tubular region of or near the heart havinga inner circumference. The method comprises inserting the distal end ofa catheter as described above into the heart. The outer circumference ofthe generally circular main region is contacted with the innercircumference of the tubular region. The electrical activity within thetubular region is mapped with the electrodes along the generallycircular main region.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a side view of an embodiment of the catheter of the invention.

FIG. 2 is a schematic side cross-sectional view of the catheter body ofFIG. 1, including the junction between the catheter body and distalshaft.

FIG. 3 is a side view of the distal shaft and mapping assembly of thecatheter according to FIG. 1.

FIG. 4 a is schematic view of the mapping assembly showing onearrangement of the ring electrodes.

FIG. 4 b is schematic view of the mapping assembly showing analternative arrangement of the ring electrodes.

FIG. 5 is a side cross-sectional view of the distal end of the mappingassembly of the catheter of FIG. 1.

FIG. 6 is an end cross-sectional view of the mapping assembly of thecatheter of FIG. 3 along line 6-6.

FIG. 7 is an end cross-sectional view of the distal shaft of thecatheter of FIG. 3 along line 7-7.

FIG. 8 is a side cross-sectional view of a control handle in accordancewith the invention.

FIG. 9 is an exploded perspective view of the interior components of thecontrol handle shown in FIG. 8.

FIG. 10 is an enlarged side cross-sectional view of the control handleof FIG. 8 showing the deflection wire adjuster and the contraction wireadjuster.

DETAILED DESCRIPTION OF THE INVENTION

According to the invention, there is provided a catheter having amapping assembly at its distal end. As shown in FIG. 1, the cathetercomprises an elongated catheter body 12 having proximal and distal ends,a control handle 16 at the proximal end of the catheter body, and amapping assembly 17 mounted at the distal end of the catheter body.

In the depicted embodiment, the catheter body 12 includes an elongatedproximal shaft 13 at its proximal end and a shorter distal shaft 14 atits distal end. With reference to FIG. 2, the proximal shaft 13comprises an elongated tubular construction having a single, axial orcentral lumen 18. The proximal shaft 13 is flexible, i.e., bendable, butsubstantially non-compressible along its length. The proximal shaft 13can be of any suitable construction and made of any suitable material. Apresently preferred construction comprises an outer wall 20 made ofpolyurethane or PEBAX. The outer wall 20 comprises an imbedded braidedmesh of stainless steel or the like, as is generally known in the art,to increase torsional stiffness of the proximal shaft 13 so that, whenthe control handle 16 is rotated, the distal shaft 14 will rotate in acorresponding manner.

The outer diameter of the proximal shaft 13 is not critical, but ispreferably no more than about 8 french, more preferably 7 french.Likewise the thickness of the outer wall 20 is not critical, but is thinenough so that the central lumen 18 can accommodate any desired wires,cables and/or tubes. The inner surface of the outer wall 20 is linedwith a stiffening tube 21 to provide improved torsional stability. Theouter diameter of the stiffening tube 21 is about the same as orslightly smaller than the inner diameter of the outer wall 20. Thestiffening tube 21 can be made of any suitable material, such aspolyimide, which provides very good stiffness and does not soften atbody temperature.

The distal shaft 14 comprises a short section of tubing having fourlumens, namely, a lead wire lumen 30, a contraction wire lumen 32, asupport member lumen 34, and a deflection wire lumen 36. The tubing ofthe distal shaft 14 is made of a suitable non-toxic material that ispreferably more flexible than the proximal shaft 13. A presentlypreferred material for the distal shaft tubing is braided polyurethane,i.e., polyurethane with an embedded mesh of braided stainless steel orthe like. The size of each lumen is not critical, but is sufficient tohouse the components extending therethrough, as discussed further below.

The useful length of the catheter, i.e., that portion that can beinserted into the body excluding the mapping assembly 17, can vary asdesired. Preferably the useful length ranges from about 110 cm to about120 cm. The length of the distal shaft 14 is a relatively small portionof the useful length, and preferably ranges from about 3.5 cm to about11 cm, more preferably from about 5 cm to about 6.5 cm.

A preferred means for attaching the proximal shaft 13 to the distalshaft 14 is illustrated in FIG. 2. The proximal end of the distal shaft14 comprises an outer circumferential notch 23 that receives the innersurface of the outer wall 20 of the catheter body 12. The distal shaft14 and catheter body 12 are attached by glue or the like. If desired, aspacer (not shown) can be provided within the proximal shaft 13 betweenthe distal end of the stiffening tube 20 and the proximal end of thedistal shaft 14 to provide a transition in flexibility at the junctionof the proximal shaft and distal shaft, which allows the junction of theproximal and distal shafts to bend smoothly without folding or kinking.An example of such a spacer is described in more detail in U.S. Pat. No.5,964,757, the disclosure of which is incorporated herein by reference.

At the distal end of the distal shaft 14 is a mapping assembly 17, asshown in FIGS. 3 to 6. The mapping assembly 17 comprises a generallystraight proximal region 38 and a generally circular main region 39. Theproximal region 38 is mounted on the distal shaft 14, as described inmore detail below, so that its axis is generally parallel to the axis ofthe distal shaft. The proximal region 38 preferably has an exposedlength, e.g., not contained within the distal shaft 14, ranging fromabout 3 mm to about 12 mm, more preferably about 3 mm to about 8 mm,still more preferably about 5 mm inch, but can vary as desired.

The generally circular main region 39 is generally traverse to thecatheter body 12. The generally circular main region 39 is preferablygenerally perpendicular to the catheter body 12. The generally circularmain region 39 can form a flat circle or can be very slightly helical,as shown in FIG. 3. The main region 39 has an outer diameter preferablyranging to about 10 mm to about 25 mm, more preferably about 12 mm toabout 20 mm. The generally circular main region 39 can curve in aclockwise direction or a counterclockwise direction.

The mapping assembly 17 is formed of a non-conductive cover 22, which ispreferably generally tubular, but can have any cross-sectional shape asdesired. The non-conductive cover 22 can be made of any suitablematerial, and is preferably made of a biocompatible plastic such aspolyurethane or PEBAX. The non-conductive cover 22 can be pre-formedinto the desired generally circular shape of the generally circular mainregion. Alternatively, the shape of the generally circular main regioncan be defined by a wire or other component extending through thenon-conductive cover 22.

In the depicted embodiment, a preformed support member 24 extendsthrough the non-conductive cover 22 to define the shape of the generallycircular main region 39. The support member 24 is made of a materialhaving shape-memory, i.e., that can be straightened or bent out of itsoriginal shape upon exertion of a force and is capable of substantiallyreturning to its original shape upon removal of the force. Aparticularly preferred material for the support member 24 is anickel/titanium alloy. Such alloys typically comprise about 55% nickeland 45% titanium, but may comprise from about 54% to about 57% nickelwith the balance being titanium. A preferred nickel/titanium alloy isNitinol, which has excellent shape memory, together with ductility,strength, corrosion resistance, electrical resistivity and temperaturestability. A series of ring electrodes 26 are mounted on thenon-conductive cover 22 of the generally circular main region 39 of themapping assembly 17, as shown in FIGS. 4 a and 4 b. The ring electrodes26 can be made of any suitable solid conductive material, such asplatinum or gold, preferably a combination of platinum and iridium, andmounted onto the non-conductive cover 22 with glue or the like.Alternatively, the ring electrodes 26 can be formed by coating thenon-conductive cover 22 with an electrically conducting material, likeplatinum, gold and/or iridium. The coating can be applied usingsputtering, ion beam deposition or an equivalent technique.

In a preferred embodiment, each ring electrode 26 is mounted by firstforming a hole in the non-conductive cover 22. An electrode lead wire 50is fed through the hole, and the ring electrode 26 is welded in placeover the lead wire and non-conductive cover 22. The lead wires 50 extendthrough the non-conductive cover 22 and into the catheter body 12. Theproximal end of each lead wire 50 is electrically connected to asuitable connector (not shown), which is connected an appropriatemonitor or other device for receiving and displaying the informationreceived from the ring electrodes 26.

The number of ring electrodes 26 on the assembly can vary as desired.Preferably the number of ring electrodes ranges from about six to abouttwenty, more preferably from about eight to about twelve. In oneembodiment, the assembly carries ten ring electrodes. The ringelectrodes 26 can be approximately evenly spaced around the generallycircular main region 39, as shown in FIG. 4 a. In a particularlypreferred embodiment, a distance of approximately 5 mm is providedbetween the centers of the ring electrodes 26.

An alternative electrode arrangement is depicted in FIG. 4 b. In thisembodiment, the mapping assembly 17 includes a series of ring electrodepairs 25. Each ring electrode pair 25 comprises two closely-spaced ringelectrodes 26. As used herein, the term “ring electrode pair” refers toa pair of ring electrodes that are arranged closer to each other thanthey are to the other adjacent ring electrodes. Preferably the distancebetween two electrodes 26 of an electrode pair 25 is less than about 3mm, more preferably less than about 2 mm, still more preferably fromabout 0.5 mm to about 1.5 mm. The number of electrode pairs 25 can varyas desired, and preferably ranges from 6 to 14 pairs, more preferably 10pairs.

In a particularly preferred embodiment, the mapping assembly carries 10pairs of electrodes with a space of approximately 1 mm between the twoelectrodes 26 of each pair 25. Preferably each ring electrode 26 isrelatively short, having a length ranging from about 0.4 mm to about0.75 mm, with the most distal ring electrode 26 c being longer than theother ring electrodes, preferably having a length ranging from about 1mm to about 1.5 mm. The longer ring electrode provides a signal to theuser when the catheter is being viewed under fluoroscopy. Specifically,because the mapping assembly is generally circular, it can be difficultfor the user to determine which electrodes are placed at a particularlocation in the heart. By having one ring electrode, such as the mostdistal ring electrode, sized differently from the other ring electrodes,the user has a reference point when viewing the catheter underfluoroscopy.

Regardless of the size and number of the ring electrodes 26, theelectrode pairs 25 are preferably approximately evenly spaced around thegenerally circular main region 39. The closely-spaced electrode pairs 25allow for more accurate detection of near field pulmonary vein potentialversus far field atrial signals, which is very important when trying totreat atrial fibrillation. Specifically, the near field pulmonary veinpotentials are very small signals whereas the atria, located very closeto the pulmonary vein, provides much larger signals. Accordingly, evenwhen the mapping array is placed in the pulmonary vein, it can bedifficult for the physician to determine whether the signal is a small,close potential (from the pulmonary vein) or a larger, farther potential(from the atria). Closely-spaced bipoles permit the physician to moreaccurately determine whether he is looking at a close signal or a farsignal. Accordingly, by having closely-spaced electrodes, one is able totarget exactly the locations of myocardial tissue that have pulmonaryvein potentials and therefore allows the clinician to deliver therapy tothe specific tissue. Moreover, the closely-spaced electrodes allow thephysician to determine the exact anatomical location of the ostium bythe electrical signal.

If desired, additional electrodes (not shown) could be mounted along thedistal shaft 14 and/or the generally straight proximal section 39.

A contraction wire 40 is provided to contract the generally circularmain region 39 to thereby reduce its diameter. The contraction wire 40has a proximal end anchored in the control handle 16, which is used tomanipulate the contraction wire as described further below. Thecontraction wire 40 extends through the central lumen 18 of the proximalshaft 13, through the contraction wire lumen 32 of the distal shaft 14and into the non-conductive cover 22. The portion of the contractionwire 40 extending through the non-conductive cover 22 is positioned onthe side of the generally circular main region 39 closer to the centerof the generally circular main region, as best shown in FIGS. 5 and 6.The center of the generally circular main region refers to the center ofthe circle formed by the generally circular main region. With thisarrangement, contraction of the generally circular main region 39 isdramatically improved over arrangements where the position of thecontraction wire 40 is not so controlled.

As shown in FIGS. 5 and 6, within the mapping assembly 17, thecontraction wire 40 extends through a plastic tube 42. In oneembodiment, the plastic tube 42 comprise three layers, including aninner layer of polyimide over which a braided layer is formed, thebraided layer comprising a braided stainless steel mesh or the like, asis generally known in the art. The braided layer enhances the strengthof the plastic tube 42, reducing the tendency for the contraction wire40 to straighten the preformed curve of the mapping assembly. A thinplastic layer of polytetrafluoroethylene is provided over the braidedlayer to protect the braided layer from getting tangled with the leadwires 50 within the non-conductive cover 22. The plastic tube 42 has aproximal end anchored to the distal end of the distal shaft 14. Thesupport member 24 extends through the plastic tube 42 with thecontraction wire 40. The distal ends of the support member 24 and thecontraction wire 40 are soldered or otherwise attached to a smallstainless steel tube 44. With this arrangement, the relative positionsof the contraction wire 40 and the support member 24 can be controlledso that the contraction wire 40 can be positioned on the side of thegenerally circular region closer to the center of the generally circularregion, as described above. The contraction wire 40 on the inside of thecurve pulls the support member 24 to the inside of the curve, enhancingcontraction of the generally circular region 39. Further, when theplastic tube 42 includes a braided layer, it keeps the contraction wire40 from tearing through the non-conductive cover 22.

A first compression coil 46 is situated within the proximal shaft 13 anddistal shaft 14 in surrounding relation to the contraction wire 40. Thefirst compression coil 46 extends from the proximal end of the proximalshaft 13 and through the contraction wire lumen 32. The firstcompression coil 46 is made of any suitable metal, preferably stainlesssteel, and is tightly wound on itself to provide flexibility, i.e.,bending, but to resist compression. The inner diameter of the firstcompression coil 46 is preferably slightly larger than the diameter ofthe contraction wire 40. The outer surface of the first compression coil46 is covered by a flexible, non-conductive sheath 68, e.g., made ofpolyimide tubing. The first compression coil 46 preferably is formed ofa wire having a square or rectangular cross-sectional area, which makesit less compressible than a compression coil formed from a wire having acircular cross-sectional area. As a result, the first compression coil46 keeps the catheter body 12, and particularly the distal shaft 14,from deflecting when the contraction wire 40 is manipulated to contractthe mapping assembly 17 as it absorbs more of the compression.

The first compression coil 46 is anchored at its proximal end to theouter wall 20 of the catheter body 12 by proximal glue joint 70 and tothe distal shaft 14 by distal glue joint 72. Both glue joints 70 and 72preferably comprise polyurethane glue or the like. The glue may beapplied by means of a syringe or the like through a hole made betweenthe outer surface of the catheter body 12 and the central lumen 18. Sucha hole may be formed, for example, by a needle or the like thatpunctures the outer wall 20 of the catheter body 12 which is heatedsufficiently to form a permanent hole. The glue is then introducedthrough the hole to the outer surface of the first compression coil 46and wicks around the outer circumference to form a glue joint about theentire circumference of the compression coil.

In the depicted embodiment, the distal end of the mapping assembly 17 issealed closed with a dome 54 of polyurethane glue or the like. A shortring 56, made of metal or plastic, and preferably polyamide, is mountedwithin the distal end of the non-conductive cover 22. The short ring 56prevents the distal end of the non-conductive cover 22 from collapsing,there by maintaining the diameter of the non-conductive cover at itsdistal end.

At the junction of the distal shaft 14 and the mapping assembly 17, thenon-conductive cover 22 is attached to the distal shaft by glue or thelike. The plastic tube 42 has its proximal end inserted and glued in thedistal end of the distal shaft 14. The glue from the plastic tube 42 canfurther serve to anchor the distal end of the first compression coil 46in place within the contraction wire lumen 32. The support member 24extends from the support member lumen 32 into the plastic tube 42 withinthe non-conductive cover 22. The proximal end of the support member 24terminates a short distance within the support member lumen 34,approximately about 5 mm, so as not to adversely affect the ability ofthe distal shaft 14 to deflect. However, if desired, the proximal end ofthe support member 24 can extend further into the catheter body 12.

The lead wires 50 attached to the ring electrodes 26 extend through thelead wire lumen 30 of the distal shaft 14, through the central lumen 18of the catheter body 12, and the control handle 16, and terminate attheir proximal end in a connector (not shown). The portion of the leadwires 50 extending through the central lumen 18 of the catheter body 12,control handle 16 and proximal end of the distal shaft 14 are enclosedwithin a protective sheath 52, which can be made of any suitablematerial, preferably polyimide. The protective sheath 52 is anchored atits distal end to the proximal end of the distal shaft 14 by gluing itin the lead wire lumen 30 with polyurethane glue or the like.

A deflection wire 64 is provided for deflection of the distal shaft 14.The deflection wire 64 extends through the proximal shaft 13, and isanchored at its proximal end to the control handle 16 and at its distalend to the distal shaft 14. The deflection wire 64 is made of anysuitable metal, such as stainless steel or Nitinol, and is preferablycoated with Teflon® or the like. The coating imparts lubricity to thepuller wire 64. The puller wire 64 preferably has a diameter rangingfrom about 0.006 to about 0.010 inch.

The deflection wire 64 extends into the deflection wire lumen 36 of thedistal shaft 14. Preferably the deflection wire 64 is anchored at itsdistal end to the sidewall of the distal shaft 14, as is generallydescribed in U.S. Pat. No. 6,371,955, the disclosure of which isincorporated herein by reference.

A second compression coil 66 is situated within the proximal shaft 13 insurrounding relation to the deflection wire 64. The second compressioncoil 66 extends from the proximal end of the proximal shaft 13 to thedistal end of the proximal shaft. The second compression coil 66 is madeof any suitable metal, preferably stainless steel, and is tightly woundon itself to provide flexibility, i.e., bending, but to resistcompression. The inner diameter of the second compression coil 66 ispreferably slightly larger than the diameter of the deflection wire 64.The Teflon® coating on the deflection wire 64 allows it to slide freelywithin the second compression coil 66. Within the proximal shaft 13, theouter surface of the second compression coil 66 is also covered by aflexible, non-conductive sheath 68, e.g., made of polyimide tubing. Thesecond compression coil 66 is anchored at its proximal end to the outerwall 20 of the catheter body 12 by the proximal glue joint 70 and to thedistal shaft 14 by the distal glue joint 72. Within the deflection wirelumen 36 of the distal shaft 14, the deflection wire 64 and secondcompression coil 66 extends through a plastic, preferably Teflon®,puller wire sheath 71, which prevents the puller wire 64 from cuttinginto the wall of the distal shaft when the distal shaft is deflected.

Longitudinal movement of the contraction wire 40 relative to thecatheter body 12, which results in contraction of the generally circularmain region 39 of the mapping assembly 17, is accomplished by suitablemanipulation of the control handle 16. Similarly, longitudinal movementof the deflection wire 64 relative to the catheter body 12, whichresults in deflection of the distal shaft 14, is accomplished bysuitable manipulation of the control handle 16. Suitable control handlesfor manipulating more than one wire are described, for example, in U.S.Pat. Nos. 6,468,260, 6,500,167, and 6,522,933, the disclosures of whichare incorporated herein by reference.

In one embodiment, the catheter includes a control handle 16 as shown inFIGS. 8 to 10. The control handle 16 includes a handle body 74 in whicha core 76 is fixedly mounted. The core has a generally cylindricaldistal region 75 and a generally cylindrical proximal region 77 having alarger diameter than the proximal region.

For longitudinal movement of the deflection wire 64, a piston 82 isslidably mounted over the distal region 77 of the core 76. The proximalend of the piston 82 is maintained within the handle body 74, and thedistal end of the piston extends outside the handle body. A thumb knob84 is mounted in surrounding relation to a portion of the distal end ofthe piston 82 so that the user can more easily move the pistonlongitudinally relative to the core 76 and handle body 74. The proximalend of the catheter body 12 is fixedly mounted to the distal end of thepiston 82 through a tip portion 78 that is mounted on the distal end ofthe piston. The proximal end of the catheter body 12 is inserted into anaxial passage 80 in the tip portion and optionally glued in place. Thepiston includes an axial passage 86 in communication with the axialpassage 80 of the tip portion 78, and the core 76 includes an axialpassage 88 in communication with the axial passage in the piston. Thelead wires 50, contraction wire 46 and deflection wire 66 that extendthrough the catheter body 12 extend out the proximal end of the catheterbody and through the axial passages in the tip portion 78, piston 82 andcore 76. The lead wires 50 can extend out the proximal end of thecontrol handle 16 or can be connected to a connector (not shown) that isincorporated into the control handle, as is generally known in the art.

The proximal end of the deflection wire 64 is anchored to the core 76.As best seen in FIG. 10, the portion of the axial passage 88 extendingthrough the proximal region 77 of the core 76 has a larger diameter thanthe portion of the axial passage extending through the distal region 75of the core 76. A deflection wire adjuster 90 is adjustably mounted, asdescribed further below, in a portion of the axial passage 88 near thedistal end of the proximal region 77 of the core 76. The deflection wireadjuster 90 has an opening 92 extending therethrough in a directiongenerally perpendicular to the axial passage 88 of the core 76. Thedeflection wire 64 extends through the opening 92 in the deflection wireadjuster 90 such that the deflection wire changes directions.

The proximal end of the deflection wire 64 is then anchored to the core76. Specifically, the distal region 77 of the core 76 includes agenerally rectangular opening 94 that extends generally parallel to theaxial passage 88 of the core. A channel 96 connects the proximal end ofthe generally rectangular opening 94 to the distal end of the portion ofthe axial passage 88 in the proximal region 75 of the core 76. Theproximal end of the deflection wire 64 extends through the channel 96and into the generally rectangular opening 94. A deflection wire anchor98, which can comprise a short piece of hypodermic stock, is fixedlyattached, for example, by crimping, to a portion of the proximal end ofthe deflection wire 64 within the generally rectangular opening 94. Thedeflection wire anchor 98 has a diameter greater than the width of thechannel 96 and thus prevents the proximal end of the deflection wire 64from being pulled through the channel, thereby anchoring the deflectionwire to the core 76.

In use, the piston 82 is moved distally relative to the handle body 74and core 76, thereby pulling the catheter body 12 distally relative tothe deflection wire 64, which is anchored to the core. As a result, thedeflection wire 64 pulls on the side of the distal shaft 14 to which itis anchored, thereby deflecting the distal shaft in that direction. Tostraighten the distal shaft 14, the piston 82 is moved proximally backto its original position relative to the handle body 74 and core 76.

Manipulation of the deflection wire adjuster 90 adjusts the amount offree play in the deflection wire 64. As noted above, the deflection wireadjuster 90 is adjustably mounted in a portion of the axial passage 88near the distal end of the proximal region 77 of the core 76. Theportion of the axial passage 88 in which the deflection wire adjuster 90is mounted includes a series of ridges 100 extending along the surfaceof the core 76, with the ridges being generally perpendicular to theaxis of the core. The deflection wire adjuster 90 carries an outwardlyextending tab 102 that fits in the spaces between the ridges 100. Thedeflection wire adjuster 90 can be moved along the length of the core 76and snapped into place by placing the tab 102 between two ridges 100. Asthe deflection wire adjuster 90 is moved proximally (away from catheterbody 12) less free play is provided for the deflection wire 64. Theprecise mechanism for adjusting the amount of free play of thedeflection wire 64 is not critical, and alternative mechanisms can beprovided. Alternatively, the deflection wire 64 can be anchored directlyto the core 76 so that it is not adjustable.

The control handle 16 is also used for longitudinal movement of thecontraction wire 40. The contraction wire 40 extends from the catheterbody 12, through the axial passage 86 in the piston 82 and through theaxial passage 88 within the distal region 75 of the core 76. Theproximal end of the contraction wire 40 is anchored to a contractionwire adjuster 104 that is slidably mounted in the core 76.

The contraction wire adjuster 104 is generally rectangular having abottom region 108 that extends downward through a slot 110 in theproximal region 77 of the core 76, the slot being in communication withthe axial passage 88 of the core. The proximal end of the contractionwire 40, which, as noted above, extends through the axial passage 88, isanchored in the contraction wire adjuster 104 in a manner very similarto the manner in which the deflection wire 64 is anchored to the core76, as described above. Specifically, a contraction wire anchor 108,which can comprise a short piece of hypodermic stock, is fixedlyattached, for example, by crimping, to a portion of the proximal end ofthe contraction wire 40 within an opening 110 in the contraction wireadjuster 104. A channel 112 connects the opening 110 to the axialpassage 88 in the core. The contraction wire anchor 98 has a diametergreater than the width of the channel 112 and thus prevents the proximalend of the contraction wire 40 from being pulled through the channel,thereby anchoring the contraction wire to the contraction wire adjuster104.

The distal end of the contraction wire adjuster 104 is adjustablyattached to a cam receiver 106. The cam receiver 106 is generallytubular, having a short slot 114 extending from its proximal end sizedto receive the distal end of the contraction wire adjuster 104. The camreceiver 106 is slidably mounted over the piston 82 and the distalregion 75 of the core 76 with the bottom portion of the contraction wireadjuster 104 positioned in the slot 114 in the core and a correspondingslot 115 in the piston.

As shown in FIG. 9, the top of the distal end of the contraction wireadjuster 104 includes a series of outwardly extending teeth 116 thatmate with a plurality of notches 118 within the slot 114 of the camreceiver 106 so that the contraction wire adjuster can be snapped intothe cam receiver. The position of the contraction wire adjuster 104relative to the cam receiver 106 can be longitudinally adjusted byrepositioning the teeth 116 relative to the notches 118, to therebyadjust the tension on the contraction wire 40.

Longitudinal movement of the cam receiver 106 and contraction wireadjuster 104 relative to the core 76, to which the catheter body 12 isindirectly mounted, results in longitudinal movement of the contractionwire 40 relative to the catheter body. Longitudinal movement of the camreceiver 106 is accomplished through a cam 120 mounted in the controlhandle 16 in surrounding relation to the piston 82 and distal region 75of the core 76. A retaining ring 121 maintains the longitudinal positionof the cam 120 relative to the handle body 74.

The cam 120 includes a ramped proximal surface 122. The cam receiver 106includes a ramped distal surface 123 and an outwardly extending tab 124at the most distal point of the ramped distal surface. The tab 124contacts the ramped proximal surface 122 of the cam 120. When the cam120 is rotated counterclockwise, the ramped proximal surface 112correspondingly rotates and pushes the cam receiver 104 proximallyrelative to the core 76 and catheter body 12. As the cam receiver 104and the attached contraction wire adjuster 104 are moved proximallyrelative to the core 76 and catheter body 12, the contraction wire 40 ispulled proximally to thereby contract the generally circular main region39 of the mapping assembly 17.

The ramped proximal surface 122 of the cam 120 includes an outwardlyextending tab 126 at its most proximal point. As the cam 120 is rotatedcounterclockwise, the tab 124 on the cam receiver 104 contacts the tab126 on the ramped proximal surface 122, thereby prohibiting furtherrotation of the cam relative to the cam receiver. As the cam 120 isrotated clockwise, the tab 126 on the ramped proximal surface 122 pushesthe tab 124 on the cam receiver 104 such that the cam receiver movesdistally, thereby releasing the tension on the contraction wire 40 sothat the generally circular main region 39 of the mapping assembly 17returns to its original configuration. As would be recognized by oneskilled in the art, the direction of the ramped proximal surface 122 canbe changed so that clockwise rotation of the cam 120 causes contractionof generally circular main region 39 of the mapping assembly 17 andcounterclockwise rotation causes it to return to its originalconfiguration. A flexible grip 128 is provided over the cam 120 for theuser to more easily and comfortably rotate the cam 120.

In use, a suitable guiding sheath is inserted into the patient with itsdistal end positioned at a desired mapping location. An example of asuitable guiding sheath for use in connection with the present inventionis the Preface™ Braiding Guiding Sheath, commercially available fromBiosense Webster, Inc. (Diamond Bar, Calif.). The distal end of thesheath is guided into one of the atria. A catheter in accordance withthe present invention is fed through the guiding sheath until its distalend extends out of the distal end of the guiding sheath. As the catheteris fed through the guiding sheath, the mapping assembly 17 isstraightened to fit through the sheath. Once the distal end of thecatheter is positioned at the desired mapping location, the guidingsheath is pulled proximally, allowing the deflectable distal shaft 14and mapping assembly 17 to extend outside the sheath, and the mappingassembly 17 returns to its original shape due to the shape-memory of thesupport member 24. The mapping assembly 17 is then inserted into apulmonary vein or other tubular region (such as the coronary sinus,superior vena cava, or inferior vena cava) so that the outercircumference of the generally circular main region 39 of the assemblyis in contact with a circumference inside the tubular region. Preferablyat least about 50%, more preferably at least about 70%, and still morepreferably at least about 80% of the circumference of the generallycircular main region is in contact with a circumference inside thetubular region.

The circular arrangement of the electrodes 26 permits measurement of theelectrical activity at that circumference of the tubular structure sothat ectopic beats between the electrodes can be identified. The size ofthe generally circular main region 39 permits measurement of electricalactivity along a diameter of a pulmonary vein or other tubular structureof or near the heart because the circular main region has a diametergenerally corresponding to that of a pulmonary vein or the coronarysinus.

The preceding description has been presented with reference to presentlypreferred embodiments of the invention. Workers skilled in the art andtechnology to which this invention pertains will appreciate thatalterations and changes in the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention.

Accordingly, the foregoing description should not be read as pertainingonly to the precise structures described and illustrated in theaccompanying drawings, but rather should be read consistent with and assupport to the following claims which are to have their fullest and fairscope

1. A mapping catheter comprising: an elongated tubular proximal shafthaving an outer wall and proximal and distal ends; a distal shaft havingproximal and distal ends, the proximal end of the distal shaft beingattached to the distal end of the proximal shaft; a mapping assembly atthe distal end of the distal shaft, the mapping assembly comprising: atubular structure comprising a preformed generally circular main regiongenerally transverse and distal to the catheter body and having an outercircumference, wherein the tubular structure comprises a non-conductivecover over at least the main region of the mapping assembly, and aplurality of electrodes carried by the generally circular main region ofthe mapping assembly; a control handle mounted at the proximal end ofthe catheter body; and a contraction wire extending through the catheterbody and non-conductive cover of the mapping assembly for contractingthe generally circular main region of the mapping assembly, thecontraction wire having a distal end anchored in the non-conductivecover and a proximal end anchored to a mechanism in the control handlethat facilitates longitudinal movement of the contraction wire relativeto the catheter body, wherein the portion of the contraction wireextending through the non-conductive cover is positioned on the side ofthe generally circular main region closer to the center of the generallycircular region.
 2. A catheter according to claim 1, wherein the portionof the contraction wire extending through the non-conductive coverextends through a plastic tube.
 3. A catheter according to claim 2,wherein the plastic tube comprises polyimide.
 4. A catheter according toclaim 2, wherein the plastic tube comprises a polyimide layer and abraided metal layer over the polyimide layer.
 5. A catheter according toclaim 1, wherein the mapping assembly further comprises a pre-formedsupport member having at least a portion extending through thenon-conductive cover.
 6. A catheter according to claim 5, wherein thepreformed support member comprises nitinol.
 7. A catheter according toclaim 5, wherein the portion of the contraction wire and the portion ofthe pre-formed support member extending through the non-conductive coverextend through a plastic tube.
 8. A catheter according to claim 7,wherein the plastic tube comprises polyimide.
 9. A catheter according toclaim 7, wherein the plastic tube comprises a polyimide layer and abraided metal layer over the polyimide layer.
 10. A catheter accordingto claim 7, wherein the contraction wire and the pre-formed supportmember each have a distal end anchored to a metal tube.
 11. A catheteraccording to claim 7, wherein the portion of the contraction wireextending through the non-conductive cover is positioned closer than thesupport member to the center of the generally circular region.
 12. Acatheter according to claim 5, wherein the portion of the contractionwire extending through the non-conductive cover is positioned closerthan the support member to the center of the generally circular region.13. A catheter according to claim 1, wherein the generally circular mainregion has an outer diameter ranging to about 10 mm to about 25 mm. 14.A catheter according to claim 1, wherein the generally circular mainregion has an outer diameter ranging to about 12 mm to about 20 mm. 15.A catheter according to claim 1, wherein the number of ring electrodesalong the generally circular main region ranges from about six to abouttwenty.
 16. A catheter according to claim 1, wherein the plurality ofelectrodes are arranged in electrode pairs.
 17. A catheter according toclaim 16, wherein the number of electrode pairs ranges from about six toabout fourteen.
 18. A catheter according to claim 1, further comprisingmeans for deflecting the distal shaft.
 19. A catheter according to claim18, wherein the deflecting means comprises a deflection wire extendingthrough the proximal shaft, the deflection wire having a distal endfixedly attached to the distal shaft and a proximal end anchored to amechanism in the control handle that facilitates longitudinal movementof the deflection wire relative to the proximal shaft.
 20. A catheteraccording to claim 1, wherein the distal shaft is more flexible than theproximal shaft.